Yes install 3 first. " is a full cumulative update"
means it is updating 3 with previous v3 updates not the whole range of .net versions.
I'd forgotten why I installed .net 3 and now you've reminded me...Nero 9. (The worst version of Nero ever produced IMHO).
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Alienware® ALX X58
OS
Win 7 Ult SP1/Win 10 Pro (all x64)
CPU
Intel® Core™ i7-975 Extreme O/C to 4.02 GHz, 8MB Cache
Motherboard
Asus® P6T Deluxe V2 X58 LGA1366
Memory
24GB Corsair Vengeance DDR3 SDRAM at 1600MHz - 6 x 4096MB